Discrete phosphor chips for light-emitting devices and related methods

ABSTRACT

In accordance with certain embodiments, phosphor chips are formed and subsequently attached to light-emitting elements.

RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalPatent Application No. 61/589,908, filed Jan. 24, 2012, and U.S.Provisional Patent Application No. 61/589,909, filed Jan. 24, 2012, theentire disclosure of each of which is hereby incorporated herein byreference.

FIELD OF THE INVENTION

In various embodiments, the present invention generally relates to lightsources, and more specifically to phosphor-converted light sources.

BACKGROUND

Light sources such as light-emitting diodes (LEDs) are an attractivealternative to incandescent and fluorescent light bulbs in illuminationdevices due to their higher efficiency, smaller form factor, longerlifetime, and enhanced mechanical robustness. However, the high cost ofLED-based lighting systems has limited their widespread utilization,particularly in broad-area general lighting applications.

The high cost of LED-based lighting systems has several contributors.LEDs are typically encased in a package, and multiple packaged LEDs areused in each lighting system to achieve the desired light intensity. Forgeneral illumination, which utilizes white light, such white light maybe generated in a number of ways. One approach is to utilize two or moreLEDs operating at different wavelengths, where the different wavelengthscombine to appear white to the human eye. For example, LEDs emitting inthe red, green and blue wavelength ranges may be utilized together. Suchan arrangement typically requires careful control of the operatingcurrents of each LED, such that the resulting combination of wavelengthsis stable over time and different operating conditions, for exampletemperature. The different LEDs may also be formed of differentmaterials, for example, AlInGaP for red LEDs and AlInGaN for blue andgreen LEDs. These different materials may have different operatingcurrent requirements as well as different temperature dependencies ofthe light output power and wavelength. Furthermore, changes inlight-output power with time may be different for each type of LED.Therefore, such systems typically utilize some form of active control ofthe current in each LED to maintain the light output power of each LEDat the desired level. In some implementations one or more sensors (forexample to sense light intensity, light color, temperature or the like)may be used to provide feedback to the current-control system, while insome other implementations the current may be adjusted over time basedon values in a look-up table. Such control systems add cost andcomplexity to lighting solutions, as well as creating additional failurepoints. A further disadvantage of multi-LED arrangements is that theytypically require some form of light combiner, diffuser or mixingchamber, so that the eye observes white light rather than the discretedifferent colors of each of the different LEDs. Such light-mixingsystems typically add cost and bulk to lighting systems as well asreducing their efficiency.

White light may also be produced in LED-based arrangements for generalillumination by means of light-conversion materials such as phosphors.LEDs generally emit in a relatively narrow wavelength range, for exampleon the order of about 20-100 nm. When broader spectra (for example“white” light) or colors different from that of the LED are desired, theLED may be combined with one or more light-conversion materials. An LEDcombined with one or more phosphors typically generates white light bycombining the short-wavelength emission from the semiconductor LED withlong-wavelength emission from the phosphor(s). This occurs because aportion of the LED light passes unconverted through the phosphor tocombine with the phosphor-converted light. Phosphors are typicallycomposed of phosphorescent particles such as Y₃Al₅O₁₂:Ce³⁺(cerium-activated yttrium-aluminum-garnet, or YAG:Ce) embedded in atransparent binder such as optical epoxy or silicone and applied as alayer.

In some implementations, the white light is a combination of the lightemitted by the light emitter and the phosphor, while in otherimplementations the white light is substantially emitted by the phosphoralone (in this case the light from the light emitter is substantiallynot visible directly by the viewer). Herein, “white light” may be whiteor any other color that is produced by a combination of light from oneor more light emitters and one or more light-conversion materials.

In some implementations, the phosphor layer absorbs a portion of theincident short-wavelength radiant flux and re-emits long-wavelengthradiant flux. For an exemplary YAG:Ce phosphor, a blue LED may have apeak wavelength of 450 nm-460 nm, corresponding to the peak of thephosphor-excitation spectrum, while the phosphor emission has abroadband spectrum with a peak at approximately 560 nm. Combining theblue LED emission with the yellow phosphor emission yields visible whitelight with a specific chromaticity (color) that depends on the ratio ofblue light to yellow light.

The geometry of the phosphor relative to the LED generally has a verystrong impact on the uniformity of the resulting light. For example, theLED may emit from both the surface and the sides of the LED, producingnon-uniform color if the phosphor composition is not uniform over theseLED surfaces. To combat this problem, the LED may be placed in areflecting cavity covered by a wavelength-converting ceramic, with thegap between the LED and the converter optionally filled with atransparent material, such that all of the light from the LED exits thecavity through the converter. However, ceramic wavelength converters maybe difficult to manufacture and brittle in thin-film form. Furthermore,they may be expensive to integrate in arrays of small LEDs.

If the thickness of the phosphor layer, formed of a uniformly dispersedphosphor in a binder, is not uniform over the surface of the LED,relatively larger amounts of blue light will be present where thephosphor-infused binder layer is thinner and relatively smaller amountsof blue light will be present where the phosphor-infused binder isthicker. While techniques such as electrophoresis may be utilized toproduce a uniform phosphor coating on an LED, electrophoresis typicallyrequires a conductive substrate or an electrically conductive coating,thus increasing cost and complexity.

Phosphor integration typically takes two forms. In one approach thephosphor is integrated in the LED package along with the LED die, whilein the other the phosphor is separate from the LED package or LED die.Packaged phosphor-converted LEDs, also known as packaged white LEDs, aretypically fabricated by mounting the LED die on a portion of the packagefollowed by integration of the phosphor. In some implementations, thephosphor is mixed with a binder or encapsulant formed over the mountedLED die and optionally over other portions of the package. It isdesirable to be able to produce packaged white LEDs with relativelynarrow distributions of electrical and optical characteristics, forexample forward voltage, luminous flux, luminous efficacy, colortemperature, color rendering index (CRI) and the like. However, there isa relatively large variation in these characteristics for the LED diesthemselves due to the growth process for the epitaxial structure and thefabrication process of the LED dies. This variation is difficult toreduce, resulting in the need to test, sort and bin the LED dies foralmost all applications. In other words, all of the LED dies are testedand grouped into bins related, typically, to forward voltage, lightoutput power and wavelength. LED dies from specific bins are thenchosen, based on the requirements of the particular application, putinto a package, followed by formation of the phosphor around all or aportion of the LED die.

As explained above, in order to produce uniform optical properties fromthe packaged white LEDs, the phosphor process typically must berelatively uniform. In some implementations the phosphor, which istypically a powder, is mixed in a liquid binder and applied to the LEDdies. It may be difficult to form a uniform layer of phosphor over theLED dies, resulting in different color temperatures for differentpackaged white LEDs. Furthermore, the phosphor powder typically has asignificantly higher density than the binder, leading to settling of thephosphor powder during manufacture and a resulting variation in colortemperature. In practice, packaged white LEDs are tested aftermanufacture and sorted and binned to produce groups of packaged whiteLEDs with uniform electrical and optical characteristics. It is clearthat this is a complicated and costly process, with the potential for asignificant portion of the output having non-optimal characteristics.

Conventional approaches may suffer from heating of the phosphor becausethe phosphor is in relatively good thermal contact with the LED die. Asthe phosphor heats up, it may lose efficiency and shift its opticalproperties, both of which are undesirable. One approach to at leastpartially mitigating heating of the phosphor is to provide increasedthermal separation of the phosphor from the LED. Such an approach issometimes called a “remote phosphor.” Remote phosphor configurations maybe incorporated into packaged white LEDs by providing some physicaland/or thermal separation of the phosphor from the LED die. One approachis to insert a portion of transparent binder or encapsulant between thephosphor-containing binder and the LED die. While such approaches atleast partially mitigate phosphor heating, they result in a more complexand costly structure.

These issues may apply to many types of phosphor-converted lightemitters, including single die-packaged devices, multiple die-packageddevices, arrays of packaged LEDs and single or arrays of unpackaged diesto which phosphor is applied.

In view of the foregoing, a need exists for structures, systems andprocedures enabling the uniform and low cost integration of phosphorswith LEDs.

SUMMARY

In accordance with certain embodiments, phosphor is molded, cured, and,if necessary, divided into free-standing solid portions (or “phosphorchips”) that are subsequently attached to light-emitting elements (LEEs)so as to receive light emitted by the LEEs. The molding process enablesfabrication of phosphor chips having very low thickness variation. Thesechips may be textured (for example, to increase light-extractionefficiency), and/or may be rectangular solids. The molding process maybe utilized to fabricate multiple phosphor chips simultaneously, eithervia use of a mold having discrete areas for containing the phosphor orby separating a larger piece of cured phosphor into multiple pieces ofdesired sizes and shapes.

As utilized herein, the term “light-emitting element” (LEE) refers toany device that emits electromagnetic radiation within a wavelengthregime of interest, for example, visible, infrared or ultravioletregime, when activated, by applying a potential difference across thedevice or passing a current through the device. Examples of LEEs includesolid-state, organic, polymer, phosphor-coated or high-flux LEDs,microLEDs (described below), laser diodes or other similar devices aswould be readily understood. The emitted radiation of a LEE may bevisible, such as red, blue or green, or invisible, such as infrared orultraviolet. A LEE may produce radiation of a spread of wavelengths. ALEE may feature a phosphorescent or fluorescent material for convertinga portion of its emissions from one set of wavelengths to another. A LEEmay include multiple LEEs, each emitting essentially the same ordifferent wavelengths. In some embodiments, a LEE is an LED that mayfeature a reflector over all or a portion of its surface upon whichelectrical contacts are positioned. The reflector may also be formedover all or a portion of the contacts themselves. In some embodiments,the contacts are themselves reflective.

A LEE may be of any size. In some embodiments, a LEEs has one lateraldimension less than 500 μm, while in other embodiments a LEE has onelateral dimension greater than 500 μm. Exemplary sizes of a relativelysmall LEE may include about 175 μm by about 250 μm, about 250 μm byabout 400 μm, about 250 μm by about 300 μm, or about 225 μm by about 175μm. Exemplary sizes of a relatively large LEE may include about 1000 μmby about 1000 μm, about 500 μm by about 500 μm, about 250 μm by about600 μm, or about 1500 μm by about 1500 μm. In some embodiments, a LEEincludes or consists essentially of a small LED die, also referred to asa “microLED.” A microLED generally has one lateral dimension less thanabout 300 μm. In some embodiments, the LEE has one lateral dimensionless than about 200 μm or even less than about 100 μm. For example, amicroLED may have a size of about 225 μm by about 175 μm or about 150 μmby about 100 μm or about 150 μm by about 50 μm. In some embodiments, thesurface area of the top surface of a microLED is less than 50,000 μm² orless than 10,000 μm². The size of the LEE is not a limitation of thepresent invention.

As used herein, “phosphor” refers to any material that shifts thewavelengths of light irradiating it and/or that is fluorescent and/orphosphorescent, and is utilized interchangeably with the term“light-conversion material.” As used herein, a “phosphor” may refer toonly the powder or particles (of one or more different types) or to thepowder or particles with the binder. The light-conversion material isincorporated to shift one or more wavelengths of at least a portion ofthe light emitted by LEEs to other desired wavelengths (which are thenemitted from the larger device alone or color-mixed with another portionof the original light emitted by the die). A light-conversion materialmay include or consist essentially of phosphor powders, quantum dots orthe like within a transparent matrix. Phosphors are typically availablein the form of powders or particles, and in such case may be mixed inbinders. An exemplary binder is silicone, i.e., polyorganosiloxane,which is most commonly polydimethylsiloxane (PDMS). Phosphors vary incomposition, and may include lutetium aluminum garnet (LuAG or GAL),yttrium aluminum garnet (YAG) or other phosphors known in the art. GAL,LuAG, YAG and other materials may be doped with various materialsincluding for example Ce, Eu, etc. The specific components and/orformulation of the phosphor and/or matrix material are not limitationsof the present invention. As used herein, a “phosphor chip” is adiscrete piece or layer of phosphor that has been fabricated and curedwhile unattached to any LEE, and that may be later coupled to an LEE by,e.g., optical bonding or via an optical adhesive.

The binder may also be referred to as an encapsulant or a matrixmaterial. In one embodiment, the binder includes or consists essentiallyof a transparent material, for example silicone-based materials orepoxy, having an index of refraction greater than 1.35. In oneembodiment the phosphor includes or consists essentially of othermaterials, for example fumed silica or alumina, to achieve otherproperties, for example to scatter light, or to reduce settling of thepowder in the binder. An example of the binder material includesmaterials from the ASP series of silicone phenyls manufactured by ShinEtsu, or the Sylgard series manufactured by Dow Corning.

Herein, two components such as light-emitting elements, opticalelements, and/or phosphor chips being “aligned” or “associated” witheach other may refer to such components being mechanically and/oroptically aligned. By “mechanically aligned” is meant coaxial orsituated along a parallel axis. By “optically aligned” is meant that atleast some light (or other electromagnetic signal) emitted by or passingthrough one component passes through and/or is emitted by the other.

In an aspect, embodiments of the invention feature an electronic devicethat includes or consists essentially of a substrate having a pluralityof conductive traces on a surface thereof, a plurality of light-emittingdiode (LED) dies, and a plurality of discrete phosphor chips eachdisposed over an LED die and positioned to receive light therefrom. Eachpair of conductive traces is separated on the substrate by a gaptherebetween. Each LED die spans a gap between conductive traces and hasfirst and second spaced-apart contacts each electrically coupled to oneof the conductive traces defining the gap. (As used herein, a “gap” is aspace between traces sufficient to prevent shorting between the traces.)Each phosphor chip is attached to an LED die by an attachment agentdiscrete from the LED die and the phosphor chip. Each phosphor chipincludes or consists essentially of (i) a light-conversion material and(ii) a binder including or consisting essentially of silicone and/orepoxy.

Embodiments of the invention feature one or more of the followingfeatures in any of a variety of combinations. The attachment agent mayinclude or consist essentially of a clip and/or a frame attached to thesubstrate. The attachment agent may include or consist essentially of anadhesion agent adhering the phosphor chip to the LED die. Thetransmittance of the attachment agent for a wavelength emitted by theLED die may be greater than 90%, or even greater than 95%. The adhesionagent may include or consist essentially of a transfer tape.

The variation in the thicknesses of the phosphor chip (i.e., chip tochip) may be less than ±5%. Each phosphor chip may absorb at least aportion of light emitted from the LED die over which it is disposed andemit converted light having a different wavelength, and the convertedlight and unconverted light emitted by the LED die may combine to formsubstantially white light. The substantially white light emittedcollectively from the different LED dies and phosphor chips may have acolor temperature variation less than four, or even less than two,MacAdam ellipses. The device may include circuitry for powering at leastone LED die and/or circuitry for controlling optical outputcharacteristics (e.g., chromaticity, luminous flux, correlated colortemperature, color point, and/or color rendering index) of at least oneLED die and the phosphor chip disposed thereover. An optical element maybe associated with at least one LED die. The first and second contactsmay be electrically coupled to conductive traces with a conductiveadhesive (e.g., an anisotropic conductive adhesive (ACA)). The ACA maybe disposed between the LED die and the substrate, and the ACA mayelectrically connect a first conductive trace only to the first contactand a second conductive trace, different from the first conductivetrace, only to the second contact. A portion of the ACA may be disposedin the gap and may substantially electrically isolate the first contactfrom the second contact.

The first and second contacts may be electrically coupled to conductivetraces with wire bonds and/or solder. Each LED die may include orconsist essentially of a bare LED die. The light-conversion material mayinclude or consist essentially of a plurality of phosphor particles. Asurface of the phosphor chip may be textured. The phosphor chip maydefine an indentation into which the LED die is at least partiallydisposed. The conductive traces may include or consist essentially ofsilver, gold, aluminum, chromium, copper, and/or carbon. The substratemay include or consist essentially of polyethylene naphthalate,polyethylene terephthalate, polycarbonate, polyethersulfone, polyester,polyimide, polyethylene, and/or paper. The reflectivity of the substratefor a wavelength emitted by the LED die and/or the phosphor chip may begreater than 80%. The transmittance of the substrate for a wavelengthemitted by the LED die and/or the phosphor chip may be greater than 80%.The LED die may include or consist essentially of a semiconductormaterial including or consisting essentially of GaN, AlN, InN, and/or analloy or mixture thereof.

In another aspect, embodiments of the invention feature an electronicdevice including or consisting essentially of a light-emitting elementand a phosphor chip disposed over the light emitting element andpositioned to receive light therefrom. The phosphor chip is attached tothe light-emitting element by an attachment agent discrete from thelight-emitting element and the phosphor chip. The phosphor chip includesor consists essentially of (i) a light-conversion material and (ii) abinder including or consisting essentially of silicone and/or epoxy.

Embodiments of the invention feature one or more of the followingfeatures in any of a variety of combinations. The light-emitting elementmay be disposed over (and even attached to) a substrate. The attachmentagent may include or consist essentially of a clip and/or a frameattached to the substrate. The attachment agent may include or consistessentially of an adhesion agent adhering the phosphor chip to thelight-emitting element. The transmittance of the attachment agent for awavelength emitted by the light-emitting element may be greater than90%, or even greater than 95%. The adhesion agent may include or consistessentially of a transfer tape.

The phosphor chip may be a rectangular solid having a thickness between5 μm and 1000 μm. A dimension of the phosphor chip perpendicular to thethickness may be between 100 μm and 5000 μm. The thickness uniformityacross the phosphor chip may be better than ±10%, or even better than±5%. A surface of the phosphor chip may be textured (e.g., roughened).The phosphor chip may define an indentation into which thelight-emitting element is at least partially disposed. The device mayinclude a substrate having first and second conductive traces on asurface thereof and separated by a gap therebetween. The light-emittingelement may have first and second spaced-apart contacts eachelectrically coupled to one of the first or second conductive traces.The first and second contacts may both be disposed on a first surface ofthe light-emitting element. The first and second contacts may beelectrically coupled to the first and second conductive traces with aconductive adhesive. The conductive adhesive may include or consistessentially of a substantially isotropic adhesive electricallyconnecting the first contact only to the first trace and the secondcontact only to the second trace, and a non-conductive adhesive materialmay be disposed in the gap. The first and second contacts may beelectrically coupled to the first and second conductive traces with ananisotropic conductive adhesive (ACA) electrically connecting the firstcontact only to the first trace and the second contact only to thesecond trace. A portion of the ACA may be disposed in the gap and maysubstantially electrically isolate the first contact from the secondcontact. The first and second contacts may be electrically coupled tothe first and second conductive traces with wire bonds and/or solder.The first and second conductive traces may include or consistessentially of silver, gold, aluminum, chromium, copper, and/or carbon.The substrate may include or consist essentially of polyethylenenaphthalate, polyethylene terephthalate, polycarbonate,polyethersulfone, polyester, polyimide, polyethylene, and/or paper. Thereflectivity of the substrate for a wavelength emitted by thelight-emitting element and/or the phosphor chip may be greater than 80%.The transmittance of the substrate for a wavelength emitted by thelight-emitting element and/or the phosphor chip may be greater than 80%.

The phosphor chip may include a plurality of discrete regions, at leastone of which includes or consists essentially of the binder and aplurality of phosphor particles. At least one portion may include orconsist essentially of only the binder. The light-emitting element mayinclude or consist essentially of a semiconductor material including orconsisting essentially of GaN, AlN, InN, and/or an alloy or mixturethereof. The light-emitting element may include or consist essentiallyof a light-emitting diode. The phosphor chip may have a curved shape.

The electronic device may include one or more additional light-emittingelements and one or more additional phosphor chips each disposed over anadditional light-emitting element and positioned to receive lighttherefrom. The phosphor chip and each additional phosphor chip may eachhave a thickness, and the variation in the thicknesses of the phosphorchips may be less than ±15%, less than ±10%, or even less than ±5%. Eachphosphor chip may absorb at least a portion of light emitted from thelight-emitting element over which it is disposed and may emit convertedlight having a different wavelength, converted light and unconvertedlight emitted by the light-emitting element combining to formsubstantially white light. The substantially white light may have acolor temperature in the range of 2000K to 10,000K. The substantiallywhite light emitted collectively from the different light-emittingelements and phosphor chips may have a color temperature variation lessthan four, or even less than two, MacAdam ellipses. The device mayinclude circuitry for powering the light-emitting element and/orcircuitry for controlling optical output characteristics (e.g.,chromaticity, luminous flux, correlated color temperature, color point,and/or color rendering index) of the light-emitting element and thephosphor chip. An optical element may be associated with thelight-emitting element.

In yet another aspect, embodiments of the invention feature a method offorming an illumination system that includes or consists essentially ofdisposing within a mold a phosphor comprising a binder and alight-conversion material, curing the phosphor, thereafter, removing thecured phosphor from the mold, and attaching at least a portion of thecured phosphor to a light-emitting element, whereby the at least aportion of the cured phosphor is positioned to receive light from thelight-emitting element.

Embodiments of the invention feature one or more of the followingfeatures in any of a variety of combinations. The at least a portion ofthe cured phosphor may be attached to the light-emitting element with anattachment agent discrete from the light-emitting element and the curedphosphor. The light-emitting element may be attached to a substrate(e.g., via an adhesive, solder, or wire bonds). The attachment agent mayinclude or consist essentially of a clip and/or a frame attached to thesubstrate. The attachment agent may include or consist essentially of anadhesion agent (e.g., an adhesive) adhering the at least a portion ofthe cured phosphor to the light-emitting element. Attaching the at leasta portion of the cured phosphor to the light-emitting element mayinclude or consist essentially of (i) applying a first portion of theadhesion agent to the light-emitting element, (ii) applying a secondportion of the adhesion agent, chemically different from the firstportion, to the at least a portion of the cured phosphor, and (iii)bringing the first and second portions of the adhesion agent intocontact. The adhesion agent may be at least partially cured via exposureto at least one of ultraviolet radiation, moisture, air, or heat. Theadhesion agent may include or consist essentially of a transfer tape.The transmittance of the adhesion agent for a wavelength emitted by thelight-emitting element may be greater than 90%, or even greater than95%.

Prior to curing the phosphor, a mold cover may be placed over thephosphor. The bottom surface of the mold cover may be substantiallyparallel to a surface of the mold on which the phosphor is disposed. Themold and the mold cover may collectively define a closed cavity (whichmay be rectilinear) in which the phosphor is disposed. The curedphosphor may be a rectangular solid having a thickness between 5 μm and1000 μm. A dimension of the cured phosphor perpendicular to thethickness may be between 10 mm and 1000 mm. The thickness uniformity ofthe cured phosphor may be better than ±15%, better than ±10%, or evenbetter than ±5%. The mold cover may have include at least one openingtherein for permitting flow of uncured phosphor therethrough. A releasematerial (e.g., a release film) may be disposed between the phosphor andat least one of (i) at least a portion of the mold or (ii) at least aportion of the mold cover. At least a portion of the mold and/or atleast a portion of the mold cover may be textured. A release material(e.g., a release film) may be disposed between the phosphor and at leasta portion of the mold. The release material may include or consistessentially of a mold release film applied to the phosphor and/or the atleast a portion of the mold, and/or the release material may betextured.

The mold may include or consist essentially of glass, metal, silicone,thermal release tape, water-soluble tape, mold release film, and/or UVrelease tape. The light-emitting element may have first and secondspaced-apart contacts. The first and second contacts may be electricallycoupled to first and second conductive traces on a substrate, the firstand second conductive traces being separated on the substrate by a gaptherebetween. The first and second contacts may be electrically coupledto the first and second conductive traces with a conductive adhesive.The conductive adhesive may include or consist essentially of asubstantially isotropic conductive adhesive electrically connecting thefirst contact only to the first trace and the second contact only to thesecond trace. A non-conductive adhesive material may be disposed in thegap. The conductive adhesive may be an anisotropic conductive adhesive(ACA) electrically connecting the first contact only to the first traceand the second contact only to the second trace. A portion of the ACAmay be disposed in the gap and may substantially isolate the firstcontact from the second contact. The electrical coupling may include orconsist essentially of wire bonding and/or soldering. The first andsecond conductive traces may include or consist essentially of silver,gold, aluminum, chromium, copper, and/or carbon. The substrate mayinclude or consist essentially of polyethylene naphthalate, polyethyleneterephthalate, polycarbonate, polyethersulfone, polyester, polyimide,polyethylene, and/or paper. The reflectivity of the substrate for awavelength emitted by the light-emitting element and/or the curedphosphor may be greater than 80%. The transmittance of the substrate fora wavelength emitted by the light-emitting element and/or the curedphosphor may be greater than 80%. The light-emitting element may includeor consist essentially of a semiconductor material including orconsisting essentially of GaN, AlN, InN, and/or an alloy or mixturethereof. The light-emitting element may include or consist essentiallyof a light-emitting diode.

The cured phosphor may absorb at least a portion of light emitted fromthe light-emitting element and may emit converted light having adifferent wavelength, converted light and unconverted light emitted bythe light-emitting element combining to form substantially white light.The substantially white light may have a color temperature in the rangeof 2000 K to 10,000 K. The cured phosphor may include or consistessentially of a plurality of discrete regions, at least one of whichincludes or consists essentially of the binder and phosphor particles.At least one of the regions may include or consist essentially of onlythe binder. A surface of the mold may include a plurality of raisedportions whereby a plurality of indentations are formed in the curedphosphor. Disposing the at least a portion of the cured phosphor overthe light-emitting element may include or consist essentially of atleast partially inserting the light-emitting element into one of thedepressions. The mold may include or consist essentially of a pluralityof discrete regions for containing phosphor, such that the curedphosphor includes or consists essentially of a plurality of phosphorchips. After removing the cured phosphor from the mold, the curedphosphor may be separated (e.g., by laser cutting, knife cutting, diecutting, and/or sawing) into a plurality of discrete phosphor chips. Oneor more of the phosphor chips may each be disposed over an additionallight-emitting element, and, for each additional light-emitting element,the phosphor chip may absorb at least a portion of light emitted fromthe additional light-emitting element and may emit converted lighthaving a different wavelength, converted light and unconverted lightemitted by the additional light-emitting element combining to formsubstantially white light. The substantially white light may have acolor temperature in the range of 2000 K to 10,000 K. The substantiallywhite light emitted collectively from the different light-emittingelements and phosphor chips may have a variation in color temperature ofless than four, or even less than two, MacAdam ellipses. The thicknessesof the phosphor chips may vary by less than ±10%, or even by less than±5%.

The light-emitting element may be electrically connected to circuitryfor powering the light-emitting element and/or to circuitry forcontrolling an optical output characteristic (e.g., luminous flux,correlated color temperature, color point, and/or color rendering index)of the light-emitting element and cured phosphor. A surface of the moldmay be stepped, whereby after curing the cured phosphor has a pluralityof portions having different thicknesses. Disposing the phosphor withinthe mold may include controlling an amount of phosphor introduced intothe mold in response to a feedback signal. The mold may include orconsist essentially of glass, metal, polyethylene terephthalate (PET),polyethylene naphthalate (PEN), plastic film, tape, adhesive on aplastic film, metal, acrylic, polycarbonate, a polymer, and/orpolytetrafluoroethylene. An optical element (e.g., a lens) may beassociated with the light-emitting element. The at least a portion ofthe cured phosphor may have a curved shape. The binder may include orconsist essentially of silicone (e.g., PDMS) and/or epoxy). Thelight-conversion material may include or consist essentially of aplurality of phosphor particles.

These and other objects, along with advantages and features of theinvention, will become more apparent through reference to the followingdescription, the accompanying drawings, and the claims. Furthermore, itis to be understood that the features of the various embodimentsdescribed herein are not mutually exclusive and can exist in variouscombinations and permutations. Reference throughout this specificationto “one example,” “an example,” “one embodiment,” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the example is included in at least one example ofthe present technology. Thus, the occurrences of the phrases “in oneexample,” “in an example,” “one embodiment,” or “an embodiment” invarious places throughout this specification are not necessarily allreferring to the same example. Furthermore, the particular features,structures, routines, steps, or characteristics may be combined in anysuitable manner in one or more examples of the technology. The term“light” broadly connotes any wavelength or wavelength band in theelectromagnetic spectrum, including, without limitation, visible light,ultraviolet radiation, and infrared radiation. Similarly, photometricterms such as “illuminance,” “luminous flux,” and “luminous intensity”extend to and include their radiometric equivalents, such as“irradiance,” “radiant flux,” and “radiant intensity.” As used herein,the terms “substantially,” “approximately,” and “about” mean ±10%, andin some embodiments, ±5%. The term “consists essentially of” meansexcluding other materials that contribute to function, unless otherwisedefined herein. Nonetheless, such other materials may be present,collectively or individually, in trace amounts.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. Also, the drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles of the invention. In the followingdescription, various embodiments of the present invention are describedwith reference to the following drawings, in which:

FIG. 1 is a flow chart for a process for forming phosphor-convertedlight-emitting devices in accordance with various embodiments of theinvention;

FIGS. 2A-2E are cross-sectional schematics of fabrication steps forphosphor chips in accordance with various embodiments of the invention;

FIGS. 3A and 3B are cross-sectional schematics of a phosphor chip withinand removed from a mold, respectively, in accordance with variousembodiments of the invention;

FIG. 4 is a schematic depiction of multiple phosphor chips fabricated inaccordance with various embodiments of the invention;

FIG. 5A is a cross-sectional schematic of phosphor chips transferred toan adhesive film in accordance with various embodiments of theinvention;

FIG. 5B is a cross-sectional schematic of light-emitting elements on asubstrate in accordance with various embodiments of the invention;

FIG. 5C is a cross-sectional schematic of an attachment agent applied tothe light-emitting elements of FIG. 5B in accordance with variousembodiments of the invention;

FIG. 5D is a cross-sectional schematic of the application of phosphorchips to the light-emitting elements and attachment agents of FIG. 5C inaccordance with various embodiments of the invention;

FIGS. 5E and 5F are cross-sectional schematics of mechanical attachmentagents attaching phosphor chips to light-emitting elements in accordancewith various embodiments of the invention;

FIG. 6 is a schematic CIE chromaticity diagram;

FIGS. 7-10 are cross-sectional schematics of light-emitting systemsincorporating multiple light-emitting devices integrated with phosphorsin accordance with various embodiments of the invention;

FIG. 11 is a cross-sectional schematic of a mold utilized forfabricating phosphor chips in accordance with various embodiments of theinvention;

FIGS. 12A and 12B are cross-sectional schematics of phosphor chipsfabricated with the mold of FIG. 11 in accordance with variousembodiments of the invention;

FIG. 13 is a cross-sectional schematic of a lighting systemincorporating multiple light-emitting devices integrated with thephosphor chips of FIG. 12B in accordance with various embodiments of theinvention;

FIGS. 14A, 14B, 15A, and 15B are cross-sectional schematics of phosphorchips in accordance with various embodiments of the invention;

FIGS. 16A-16D are cross-sectional schematics of phosphor chipsfabricated with different thicknesses from the same mold in accordancewith various embodiments of the invention;

FIG. 17 is a cross-sectional schematic of an apparatus for controllingthe thickness of a phosphor chip in accordance with various embodimentsof the invention;

FIG. 18 is a cross-sectional schematic of a phosphor chip havingmultiple regions of different phosphors in accordance with variousembodiments of the invention;

FIG. 19 is a plan-view schematic of a lighting apparatus incorporatingmultiple lighting devices and phosphor chips in accordance with variousembodiments of the invention; and

FIGS. 20-22 are cross-sectional schematics of lighting apparatusesincorporating multiple lighting devices and phosphor chips in accordancewith various embodiments of the invention.

DETAILED DESCRIPTION

FIG. 1 is a flow chart depicting a process 100 for forming aphosphor-converted LEE in accordance with an embodiment of the presentinvention. Process 100 is shown as having six steps; however, this isnot a limitation of the present invention and in other embodiments theinvention includes more or fewer steps and/or the steps are performed indifferent order. Process 100 begins with a step 110, in which a mold isprovided. In a step 120, a phosphor is provided. In a step 130, thephosphor is formed in the mold. In a step 140, the phosphor is cured. Ina step 150, the phosphor is removed from the mold. In a step 160, thephosphor is formed over one or more LEEs. Optionally, the phosphor maybe separated into multiple pieces. This step may occur before or afterstep 150, removing the phosphor from the mold, and may also occur afterpartially curing the phosphor in step 140.

FIGS. 2A-2E depict a portion of process 100 in accordance with variousembodiments of the present invention. FIG. 2A depicts a surface 200 of amold 230. Surface 200 may incorporate one or more bounding faces 220,which may be formed by a second layer of a material 210 as shown in FIG.2B. In one embodiment, bounding faces 220 are formed by forming a recessin mold 230, as shown in FIG. 2C. In FIGS. 2B and 2C the bounding faces220 are shown as perpendicular or substantially perpendicular to surface200; however, this is not a limitation of the present invention, and inother embodiments bounding faces 220 form any angle with surface 200.Mold 230 may include or consist essentially of one or more materials,for example glass, PET, PEN, plastic film, tape, adhesive on plasticfilm, metal, acrylic, polycarbonate, polymers, Teflon, or the like. Thematerial of the mold is not a limitation of the present invention. Insome embodiments, mold 230 is substantially rigid, while in others mold230 is flexible. In some embodiments, it is advantageous for mold 230 tofeature a “non-stick” material such as Teflon, or to have a “non-stick”coating over the surface or portion of the surface that may come incontact with a phosphor (for example the binder in the phosphor) so thatthe phosphor does not stick to mold 230. In some embodiments, mold 230includes a layer of material on surface 200 and/or bounding faces 220that does not adhere well to the binder material. In some embodiments,mold 230 includes or consists essentially of a water-soluble material,or mold 230 may be partially or completely lined with a water-solublematerial to aid in the release of mold 230 from the material formed inmold 230. In one embodiment, mold 230 includes or is partially or fullylined with a water-soluble tape, for example 3M type 5414. In someembodiments, mold 230 is transparent to light, for example to visible orUV radiation. In some embodiments, the height of bounding faces 220ranges from about 10 μm to about 1000 μm; however, the height ofbounding faces 220 is not a limitation of the present invention, and inother embodiments bounding faces 220 have any height. In someembodiments, the area of mold 230 is in the range of about 0.25 mm² toabout 400 cm²; however, the area of mold 230 is not a limitation of thepresent invention, and in other embodiments the area of mold 230 issmaller or larger.

The next step in process 100 is to provide a phosphor. In oneembodiment, the phosphor includes or consists essentially of a phosphorand a binder. In some embodiments the phosphor and binder are mixed, forexample in a centrifugal mixer, with or without a partial vacuum overthe mixture.

In step 130 the phosphor is formed in the mold, as shown in FIG. 3. FIG.3 shows mold 230 from FIG. 2C having bounding faces 220 and surface 200,as well as a phosphor 310 with a top surface 320 and a bottom surface330. Phosphor 310 may be formed in the mold by a variety of techniques,for example dispensing, pouring, injecting, etc. The method of formationof phosphor 310 in mold 230 is not a limitation of the presentinvention. In some embodiments, mold 230 is positioned such that surface200 is level, such that when phosphor 310 is formed in mold 230, surface320 and surface 330 are parallel, forming a thin layer of phosphor 310that has a uniform or substantially uniform thickness across all or mostof the area of phosphor 310. In some embodiments, mold 230 includes aflat surface, such as shown in FIG. 2A, and formation of phosphor 310may be accomplished using a Mayer bar or draw-down bar, to achieve auniform layer of phosphor 310. However it is formed, in one aspect ofthe present invention mold 230 is level or substantially level andgravity is used to automatically produce phosphor layer 310 with auniform or substantially uniform thickness. In various embodiments ofthe invention, the thickness uniformity of phosphor 310 is within about±15%, within about ±10%, within about ±5% or within about ±1%. In oneembodiment, phosphor 310 has a thickness in the range of about 5 μm toabout 500 μm; however, the thickness of phosphor 310 is not a limitationof the present invention and in other embodiments phosphor 310 isthinner or thicker. In one embodiment, the time between mixing aphosphor 310 including binder and phosphor powder and forming phosphor310 in mold 230 is relatively short, compared to the time required forsettling of the powder in the binder, such that the phosphor and binderform a uniform and homogeneously distributed or substantially uniformand homogeneously distributed combination of phosphor powder in thebinder. In various embodiments of the invention, the compositionaluniformity of phosphor 310, that is the distribution of phosphor powderin the binder, is uniform to within about ±15%, within about ±10%,within about ±5% or within about ±1%. In some embodiments utilizingmixtures of phosphor and powder, settling starts to occur within about10 to about 30 minutes, while formation of phosphor 310 in mold 230occurs within about 0.25 minutes to about 5 minutes.

In some embodiments, a mold top or mold cover 231 (as shown in FIG. 2D)may be formed over mold 230. Mold top 231 may be formed over mold 230before or after formation of phosphor 310. In some embodiments, asurface 232 of mold top 231 is parallel or substantially parallel tosurface 200 of mold 230, such that after curing, a phosphor 311 (shownin FIG. 3) has a substantially uniform thickness substantiallycontrolled by the distance between surfaces 200 and 232. In someembodiments, mold 230 is filled or overfilled with phosphor 310, suchthat when using mold top 231 there is an amount of phosphor 310 that isin excess of the amount required to fill the mold cavity defined by mold230 and mold top 231. In some embodiments, excess phosphor 310 issqueezed out between mold top 231 and mold 230, as shown in FIG. 2E.

In some embodiments of this example, one or more portions of mold 230and/or mold top 231 have one or more openings or through-holes 233 thatprovide an overflow pathway for phosphor 310 during the mating process,as shown in FIG. 2E. When mold 230 and mold top 231 are mated, hole 233provides a pathway for excess phosphor 310 to escape, thereby permittingthe manufacture of a uniform phosphor plate 311, without excess phosphorsqueezing out from the sides of the mold. In some embodiments, thisprovides improved control of the thickness of phosphor 311 as well as amore reproducible manufacturing process. This approach may be applied toother embodiments, for example where the mold top 231 is formed prior toformation of phosphor 310 in the mold.

In step 140, phosphor 310 is cured. Curing may include or consistessentially of heating, exposure to radiation of various sources, forexample visible, UV and/or IR light, or chemical curing (i.e., additionof an additional agent that promotes cross-linking in the binder). Inone embodiment, phosphor 310 is cured by UV or other radiation and mold230 is transparent to such radiation. In one embodiment, mold 230 isheld within the curing equipment prior to or just after step 130 ofFIG. 1. In some embodiments utilizing mixtures of phosphor and powder,settling starts to occur within about 10 to about 30 minutes, whilecuring of phosphor 310 in mold 230 occurs within about 0.10 minutes toabout 5 minutes. In various embodiments of the invention, steps 130 and140 collectively consume less than about 10 minutes, less than about 5minutes, or less than about 1 minute. In some embodiments, the curingstep 140 includes or consists essentially of multiple sub-curing steps.For example, a first sub-curing step may be performed to “freeze” thephosphor particles in the matrix, and this may be followed by a secondsub-curing step to fully cure the binder.

In step 150 the cured phosphor 310, now identified as phosphor 311, isremoved from mold 230. At this point in the process, phosphor 311 is asolid having parallel or substantially parallel face 320 and face 330,where the thickness bounded by face 320 and face 330 is uniform orsubstantially uniform. In one embodiment, the thickness uniformity ofphosphor 311 is within about ±15%, within about ±10%, within about ±5%or within about ±1%. In one embodiment, phosphor 311 has a thickness inthe range of about 5 μm to about 500 μm; however, the thickness ofphosphor 311 is not a limitation of the present invention, and in otherembodiments phosphor 311 is thinner or thicker. In one embodiment, thecompositional uniformity of phosphor 311, i.e., the distribution ofphosphor powder in the binder, is uniform to within about ±15%, withinabout ±10%, within about ±5% or within about ±1%. In some embodiments,the area of phosphor 311 is in the range of about 0.25 mm² to about 400cm²; however, the area of phosphor 311 is not a limitation of thepresent invention, and in other embodiments the area of phosphor 311 issmaller or larger.

In some embodiments, phosphor 311 is separated into multiple piecesprior to use. Separation of phosphor 311 may be performed via any ofmultiple techniques, for example laser cutting, cutting with a knife,die cutting, saw cutting, or the like. In some embodiments, separationof phosphor 311 into multiple pieces is done before step 150 (removal ofphosphor from mold) while in other embodiments separation of phosphor311 into multiple pieces is done after step 150. FIG. 4 shows aschematic of phosphor 311 separated into multiple pieces 312. Phosphorpieces 312 are shown in FIG. 4 as being square and having sidewallsperpendicular to surface 320. However, this is not a limitation of thepresent invention, and in other embodiments phosphor pieces 312 arerectangular, hexagonal, circular, triangular or any arbitrary shape,and/or have sidewalls forming any angle with respect to the surface 320of phosphor piece 312.

In some embodiments, phosphor 311 is transferred from mold 230 to aflexible and optionally adhesive film 510, as shown in FIG. 5A. Such atransfer may be performed, for example, by peeling phosphor 311 off ofmold 230 and placing it on film 510. In one embodiment, film 510includes or consists essentially of a thermal release adhesive, while inanother embodiment film 510 includes or consists essentially of a UVrelease adhesive. In some embodiments, film 510 is the same as orsimilar to dicing or transfer tapes used in the semiconductor industryfor singulation and/or transfer of dies, e.g., Revalpha from Nitto DenkoCorporation or tapes from Semiconductor Equipment Corporation. In someembodiments, mold 230 includes or consists essentially of film 510, thatis, the phosphor is formed directly on film 510 instead of being formedin mold 230 and transferred to film 510. In one embodiment, film 510includes or consists essentially of a water-soluble tape, for example 3Mtype 5414.

In some embodiments, mold 230 includes multiple depressions or wellsinto which phosphor 310 is formed, permitting formation of structuressuch as that shown in FIG. 4 (i.e., multiple separate sections), withoutthe necessity of cutting cured phosphor 311 into pieces 312. In someembodiments, a cover or plate is formed over mold 230 after provision ofphosphor 310 over mold 230. In some embodiments, the cover or plate actsto form a smooth top surface 320 and to help produce a uniform thicknessof phosphor 311.

The process detailed above generally produces uniform or substantiallyuniform phosphor pieces or chips 312. These may then be applied to LEEs,for example to achieve white light emission from the combination of theLEE and the phosphor chip; at least a portion of the light emitted bythe LEE is absorbed by phosphor chip 312, and at least a portion of theabsorbed light is re-emitted at a different wavelength. In oneembodiment, white light is formed from a structure including orconsisting essentially of a LEE emitting in the blue wavelength range(about 440 μm to about 470 μm), for example a blue LED and one or morephosphors emitting in the yellow-red range, such that the combinationproduces light that appears white to the eye. In one embodiment, thewhite light is visible light with a spectral power distribution whosechromaticity is close to the blackbody locus in the CIE 1931 xy orsimilar color space. In one embodiment, white light may have acorrelated color temperature (CCT or color temperature) in the range ofabout 2000K to about 10,000K. Embodiments of the invention are notlimited to materials, processes and structures that produce white light;in other embodiments these materials, structures and processes are usedto produce any color light.

Application of phosphor chip 312 to the LEE may be performed in any of avariety of ways and with any of a number of attachment agents (such asclips, frames, or adhesion agents). In one embodiment phosphor chips 312are picked from the structure shown in FIG. 5A and placed on the LEEsusing a conventional pick-and-place tool. In one embodiment the processstarts with an LEE 520 on a substrate 521 as shown in FIG. 5B. Anadhesive agent 530 is then formed over LEE 520, as shown in FIG. 5C. Asmay be seen from FIG. 5C, different amounts of adhesive agent may beapplied for different needs. For example if phosphor chip 312 issignificantly larger than LEE 520 and is designed to overlap LEE 520, asshown in the example on the left of FIG. 5D, then a larger amount ofadhesive agent may be advantageous compared to the amount used for asmaller phosphor chip, as shown on the right of FIG. 5D. Phosphor chips312 may be transferred from the structure shown in FIG. 5A to that shownin FIG. 5D using a variety of means. In one embodiment phosphor chips312 may be treated similarly to semiconductor chips and transferredusing commonly available semiconductor chip or package transfer tools,such as pick and place tools. FIG. 5D shows transfer of phosphor chips312 from the chip substrate 521 to the LEE. While FIGS. 5C and 5D depictthe adhesive agent as applied to all exposed surfaces of the LEEs 520,in some embodiments the adhesive agent is applied only to a portion orthe entirety of the top surface of an LEE 520. In some embodiments, theadhesive agent may include or consist essentially of a transfer tapesuch as, e.g., 467, 7995, or 7962 tapes available from 3M. In preferredembodiments, the transmittance of the attachment agent (particularly ifthe attachment agent is an adhesive agent) for a wavelength emitted bythe LEE 520 is greater than 90%, or even greater than 95%.

In one embodiment phosphor chip 312 is applied to the LEE using anadhesion agent that is distinct from phosphor chip 312 and/or from theLEE. In one embodiment an adhesive or glue is disposed between the LEEand phosphor chip 312. In various embodiments this may be done using aliquid adhesive which may be sprayed, dispensed, screen printed, orstencil printed onto the LEE prior to application of phosphor chip 312.In one embodiment an adhesion agent may be applied to one side ofphosphor chip 312 and that side applied to the LEE. Application of theadhesion agent to phosphor chip 312 may be done in ways similar toapplication of the adhesion agent to the LEE, as described herein. Inother embodiments the adhesion agent may be applied to the curedphosphor before singulation into discrete chips.

In some embodiments the adhesion agent may include a curable adhesionagent, where the curing is activated by exposure to air, radiation, forexample heat, UV radiation or the like, or moisture or by other means.In some embodiments the adhesion agent may have more than one component.For example in one embodiment a two-component adhesion agent may beutilized by application of a first part to phosphor chip 312 and asecond part to the LEE, where the agent becomes adhesive when the twoparts are brought in contact. In some embodiments such an approach mayrequire additional activation for curing, while in others that is notrequired. Advantageously, a two-component system may be used in oneembodiment by application of a first component to the phosphor beforesingulation into chips. In a similarly advantageous fashion, radiationor otherwise activated adhesives may be applied to the phosphor beforesingulation.

Adhesion agents preferably have high transparency to all or asignificant portion of the wavelengths and/or radiant flux emitted bythe LEE. In some embodiments the adhesion agent may be the same orsimilar material that is used as the binder or matrix for the phosphorchip.

In some embodiments of the present invention phosphor chip 312 may beheld in place mechanically, for example by fitting into a frame or clipon the substrate surrounding the LEE, as shown in the examples in FIGS.5E and 5F. FIGS. 5E and 5F depict a mechanical attachment agent 540 (inthe form of a frame in FIG. 5E and a clip in FIG. 5F) attaching thephosphor chip 312 to the underlying LEE 520. The examples shown in FIGS.5E and 5F are exemplary and are not meant to be limitations of thepresent invention.

In some embodiments of the present invention a transparent transfer tapemay be applied to the phosphor before singulation into chips. In someembodiments a liner covers the side of the transfer tape opposite thephosphor. In some embodiments the phosphor and transfer tape aresingulated in one step, while in other embodiments this is a multi-stepprocess. Singulation may be accomplished in some embodiments using meansdescribed herein for phosphor singulation, for example laser cutting,knife cutting, shearing, rotary wheel cutting or the like. The method ofsingulation is not a limitation of the present invention. In embodimentswhere a liner is present, the liner is removed and the phosphor chipadhered to the LEE. Transfer tapes preferably have high transparency toall or a significant portion of the wavelengths and/or radiant fluxemitted by the LEE.

In some embodiments high transparency means a transmissivity greaterthan 90% for all of the radiant flux incident on it from the LEE. Insome embodiments high transparency means a transmissivity greater than95% for all of the radiant flux incident on it from the LEE. In someembodiments high transparency means a transmissivity of greater than 90%for wavelengths in the range of about 420 nm to about 700 nm. In someembodiments high transparency means a transmissivity of greater than 95%for wavelengths in the range of about 420 nm to about 700 nm.

Advantageously, embodiments of the present invention produce phosphorchips 312 that have uniform or substantially uniform thickness anduniform or substantially uniform distribution of phosphor particles inthe binder. The thickness and distribution, or loading, of the phosphorparticles may have a strong impact on the uniformity of the colortemperature of the light. In systems with multiple LEEs, and inparticular arrays with tens to thousands of LEEs, it may be otherwisedifficult to achieve a uniform phosphor coating over all of the LEEs,resulting in non-uniform color temperature. FIG. 6 shows a schematic ofthe CIE chromaticity diagram with the blackbody locus 610 and an ellipse620 representing one or more MacAdam ellipses. The major axis of MacAdamellipse 620 is labeled as 640 while the minor axis is labeled as 630. AMacAdam ellipse represents a region of colors on the chromaticity chartand a one-step MacAdam ellipse represents the range of colors around thecenter of the ellipse that are generally indistinguishable to theaverage human eye, from the color at the center of the ellipse. Thecontour of a one-step MacAdam ellipse therefore represents the justnoticeable differences of chromaticity.

Multiple-step MacAdam ellipses that encompass larger ranges of coloraround the center point may be constructed. The black body locus is ingeneral aligned with the major axis of a MacAdam ellipse, meaning thatthe eye is less sensitive to color differences along the black bodyline, which equates to red/blue shifts, than to differencesperpendicular to the black body line, which equates to a green/magentashift. Furthermore, with respect to phosphor-converted white lightsources, the variation in the minor axis direction 630 is in largemeasure determined by the LEE (typically a LED) wavelength variation,while the variation in the major axis direction 640 may be determined bythe phosphor concentration and thickness. While there are manyrecommendations as to how tight the color temperature uniformity shouldbe (as measured by MacAdam ellipses), it is clear that a variationencompassed within a smaller step number of MacAdam ellipses (smallerellipse) is generally more uniform than one encompassed within a largerstep number of MacAdam ellipses (larger ellipse). For example, afour-step MacAdam ellipse encompasses about a 300K color temperaturevariation along the black body locus, centered at 3200K, while atwo-step MacAdam ellipse encompasses about a 150K color temperaturevariation along the black body locus, centered at 3200K.

The importance of uniform thickness and phosphor concentration inphosphor chips 312 may be observed in relation to the MacAdam ellipse onthe chromaticity chart of FIG. 6. Since the major axis length is largelydetermined by the phosphor concentration and thickness, variations inthese parameters result in an increase in the major axis of the MacAdamellipse and thus an increase in the variation in color temperature. Theaforementioned technique for fabrication of uniform phosphor chips 312,when used in a phosphor-converted light source, typically results in areduction in the variation in color temperature and thus a more uniformcolor temperature light source, both within a lighting system featuringan array of phosphor-converted LEEs and between such lighting systems.The use of the aforementioned LEEs in lighting systems typically permitsthe manufacture of large numbers of lighting systems having uniformcolor temperatures.

FIG. 7 depicts one embodiment of such a lighting system 700, whichincludes multiple LEEs 710 formed over an LEE substrate 720. The LEEs710 are electrically coupled together by conductive traces 730 formedover substrate 720. System 700 optionally includes transparent material740 formed between all or some phosphor chips 312 and LEEs 710. In oneembodiment, transparent material 740 includes or consists essentially ofthe binder or matrix material described previously (and substantiallylacks phosphor particles), and acts to provide improved optical couplingbetween LEEs 710 and phosphor chips 312, as well as to increase lightextraction from LEEs 710 by reducing total internal reflection (TIR)losses in LEEs 710.

LEE substrate 720 may include or consist essentially of asemicrystalline or amorphous material, e.g., polyethylene naphthalate(PEN), polyethylene terephthalate (PET), acrylic, polycarbonate,polyethersulfone, polyester, polyimide, polyethylene, and/or paper. LEEsubstrate 720 may also include or consist essentially of a rigid orflexible circuit board, for example FR4, metal core printed circuitboard (MCPCB), polyimide or the like. LEE substrate 720 may besubstantially flexible, substantially rigid or substantially yielding.In some embodiments, the substrate is “flexible” in the sense of beingpliant in response to a force and resilient, i.e., tending toelastically resume an original configuration upon removal of the force.A substrate may be “deformable” in the sense of conformally yielding toa force, but the deformation may or may not be permanent; that is, thesubstrate may not be resilient. Flexible materials used herein may ormay not be deformable (i.e., they may elastically respond by, forexample, bending without undergoing structural distortion), anddeformable substrates may or may not be flexible (i.e., they may undergopermanent structural distortion in response to a force). The term“yielding” is herein used to connote a material that is flexible ordeformable or both.

LEE substrate 720 may include multiple layers, e.g., a deformable layerover a rigid layer, for example, a semicrystalline or amorphousmaterial, e.g., PEN, PET, polycarbonate, polyethersulfone, polyester,polyimide, polyethylene, paint, plastic film and/or paper formed over arigid substrate for example including, acrylic, aluminum, steel and thelike. Depending upon the desired application for which embodiments ofthe invention are utilized, LEE substrate 720 is substantially opticallytransparent, translucent, or opaque. For example, LEE substrate 720 mayexhibit a transmittance or a reflectivity greater than about 80% foroptical wavelengths ranging between approximately 400 nm andapproximately 700 nm. In some embodiments, LEE substrate 720 exhibits atransmittance or a reflectivity of greater than about 80% for one ormore wavelengths emitted by LEE 710 and/or phosphor chip 312. LEEsubstrate 720 may also be substantially insulating, and may have anelectrical resistivity greater than approximately 100 ohm-cm, greaterthan approximately 1×10⁶ ohm-cm, or even greater than approximately1×10¹⁰ ohm-cm.

Conductive traces 730 may include or consist essentially of anyconductive material, for example metals such as gold, silver, aluminum,copper and the like, conductive oxides, carbon, etc. Conductive traces730 may be formed on LEE substrate 720 by a variety of means, forexample physical deposition, plating, lamination, lamination andpatterning, electroplating, printing or the like. In one embodiment,conductive traces 730 are formed using printing, for example screenprinting, stencil printing, flexo, gravure, ink jet, or the like.Conductive traces 730 may include or consist essentially of atransparent conductor, for example, a transparent conductive oxide suchas indium tin oxide (ITO). Conductive traces 730 may include or consistessentially of one or more materials. Conductive traces 730 mayoptionally feature stud bumps to aid in electrical coupling ofconductive traces 730 to LEEs 710. Conductive traces 730 may have athickness in the range of about 0.05 μm to about 250 μm. While thethickness of one or more of the conductive traces 730 may vary, thethickness is generally substantially uniform along the length of theconductive trace 730 to simplify processing. However, this is not alimitation of the present invention and in other embodiments theconductive trace thickness or material varies.

In one embodiment, one or more LEEs 710 are electrically coupled toconductive traces 730 using conductive adhesive, e.g., an isotropicallyconductive adhesive and/or an anisotropically conductive adhesive (ACA),as described in U.S. patent application Ser. No. 13/171,973, filed Jun.29, 2011, the entire disclosure of which is incorporated by referenceherein. An ACA is a material that permits electrical conduction only inthe vertical direction but insulates the conductive trace 730 from eachother. As used here, ACA may be provided in any form, for example paste,gel, liquid, film, or otherwise. ACAs may be utilized with or withoutstud bumps in accordance with embodiments of the present invention.

Various embodiments may utilize one or more other electricallyconductive adhesives, e.g., isotropically conductive adhesives, inaddition to or instead of one or more ACAs. Various embodiments mayutilize wire bonding, thermosonic bonding, ultrasonic bonding, or solderas the method to connect LEEs 710 to conductive traces 730. The methodof attachment and/or electrical coupling of LEE 710 to conductive traces730 are not a limitation of the present invention.

A further advantage of the aforementioned approach is that it is has arelatively high efficiency of use of the phosphor, which may berelatively expensive. In large arrays of LEEs, the LEE pitch (distancebetween LEEs) may be on the order of about 3 mm to about 20 mm. In someembodiments, a large array has an area in the range of about 100 cm² toabout 3600 cm² or to about 10,000 cm² or larger. If the entire area wereto be covered by phosphor, this would require a very large amount ofphosphor, most of which would not be optically active. As an example,assume an array size of about 2500 cm² and a pitch of about 5 mm; thisresults in an array of 100×100 LEEs, for a total of 10,000 LEEs. If eachLEE is associated with a phosphor chip having a size of about 1.5mm×about 1.5 mm, this results in a phosphor area for the presentinvention of about 225 cm² (excluding kerf loss). This is about a 10×reduction in the area of phosphor required for such an array. As the LEEpitch increases, the area reduction increases.

The structure shown in FIG. 7 may be manufactured by a variety oftechniques. In one embodiment, after placement of LEEs 710, a portion oftransparent material or binder 740 is dispensed over all of or a portionof an LEE 710. Phosphor chip 312 is then placed over transparentmaterial 740 and transparent material 740 is cured, for example usingheat or UV radiation. In one embodiment, phosphor chip 312 is placedover transparent material 740 using a conventional pick-and-place tool,by picking the phosphor chip from the structure shown in FIG. 5A. Insome embodiments, film or tape 510 includes or consists essentially of aheat- or UV-release tape, such that the tackiness level of the adhesiveis greatly reduced upon heating or exposure to UV radiation. Such areduction in tackiness leads to easier removal (picking) from film 510during the pick-and-place operation. In some embodiments, picking may beaided by the use of an ejector pin that pushes up from underneath film510, to help remove phosphor chip 312 from film 510. In anotherembodiment, a portion of transparent material or binder 740 is dispensedover all or a portion of phosphor chip 312 prior to placement over LEE710.

In the embodiment shown in FIG. 7, phosphor chip 312 is physicallyand/or thermally separated from LEE 710, resulting in a “remotephosphor” configuration. Such a configuration may result in less heatingof phosphor chip 312 during operation, leading to increased efficiencyand longer life. In some embodiments, material 740 is not utilized andthe phosphor chip 312 is not spaced away from the LEE 710.

In the embodiment shown in FIG. 7, phosphor chip 312 extends beyond theedge of LEE 710. The degree of the overhang may be adjusted to achievefull or the desired level of coverage of the blue emission by phosphorchip 312, in order to minimize or eliminate direct emission from LEE710. As shown in FIG. 8, in another embodiment phosphor chip 312completely covers the top and sides of LEE 710. In another embodiment,LEE 710 is thin enough (identified as LEE 910 in FIG. 9) such that fullcoverage of LEE 710 by phosphor chip 312 may be accomplished with anessentially flat phosphor chip 312, as shown in FIG. 9. The structure inFIG. 9 may or may not include transparent material 740. Thin LEE 910 maybe formed by removing all or a portion of the growth substrate, forexample by removing the sapphire or silicon carbide substrate upon whichGaN-based LEEs are typically grown. In some embodiments the sapphire orSiC substrate is removed by laser lift-off (LLO) or mechanical orchemical mechanical polishing (CMP). In another embodiment, LEE 910 isgrown on a silicon substrate and the silicon substrate removed by wetchemical etching, dry chemical etching, lapping, polishing, CMP,undercut etching, any combinations of these or the like. In someembodiments, LEEs 710 and/or 910 have a reflective coating over all or aportion of the surface adjacent to substrate 720 and conductive traces730. The reflective coating may be reflective to a wavelength of lightemitted by LEE 710 and/or 910 and/or phosphor chip 312.

In some embodiments, LEEs 710 and/or 910 may be formed in an indentationor well 1010 such that all or a portion of an LEE 710 and/or LEE 910 iswithin well 1010, as shown in FIG. 10. Well 1010 may be fully orpartially filled with transparent binder 740. Well 1010 may be formed aspart of LEE substrate 720, or may be formed by the addition of one ormore layers 1020, having through-holes that correspond to the positionof LEE 710. Phosphor chip 312 may overhang well 1010 as shown in FIG.10, or may fit inside well 1010.

In the examples above, the phosphor chip 312 is generally shown as auniform rectangular solid having substantially smooth surfaces; however,this is not a limitation of the present invention, and in otherembodiments phosphor chip 312 is shaped in any manner and/or may haveroughened, patterned or textured surfaces, with such surface features ina regular, periodic or random pattern. In some embodiments, shapingand/or patterning or texturing of the surface is achieved during theformation or molding process, while in other embodiments shaping and/orpatterning or texturing are performed after the phosphor is molded orafter it is cured or partially cured.

In another embodiment, one or more surfaces of phosphor chip 311 arenon-smooth, for example roughed, textured or patterned. In oneembodiment, the non-smooth surface reduces total internal reflection(TIR) within phosphor chip 311 and achieves improved light extraction.In another embodiment, phosphor chip 311 is shaped in a lens shape. Sucha lens may be a hemisphere, a paraboloid, a Fresnel optic or any othershape. In one embodiment, such a lens may be used to achieve a specificand desired light-distribution pattern. In one embodiment, phosphor chip311 includes a photonic crystal formed on all or a part of the surfaceof phosphor chip 311, for example on all or a portion of the top surfaceof phosphor chip 311. In one embodiment, the photonic crystal increasesthe intensity of light exiting phosphor chip 311 in a particulardirection.

In one embodiment, mold 230 features raised regions or bumps 1110 havingsubstantially the size of LEE 710 or larger, as shown in FIG. 11. Such amold produces phosphor 311 with indentations or wells 1210. Afterseparation, phosphor chips 312 having indentations 1210 may be formed,as shown in FIGS. 12A and 12B. Phosphor chips 312 with indentations 1210may now be placed over LEEs 710 as shown in FIG. 13 (conductive traces730 not shown for clarity). Indentations 1210 may fit relatively snuglyover LEE 710 or may be large enough to leave space between phosphor chip312 and LEE 710. Transparent material 740 may optionally be formedbetween phosphor chip 312 and LEE 710 (not shown in FIG. 13). In someother embodiments of this aspect of the invention, mold 230 featuresmultiple depressions into which phosphor 310 may be formed. The regionof mold 230 between the depressions corresponds to the eventual positionof LEE 710, and after curing and separation phosphor chips 312 withdepressions 1210, similar to those shown in FIG. 12 are formed. In someembodiments, such a process forms phosphor chips 312 similar to thoseshown in FIG. 12 but having a portion of phosphor 311 overhanging theregions formed by the depressions in mold 230, forming a shape similarto the Greek letter pi.

In another embodiment, phosphor 310 and 311 and phosphor chip 312include or consists essentially of multiple discrete layers. In oneembodiment, a first layer 1420 includes or consists essentially of atransparent material such as binder or matrix material 740 and a secondlayer 1410 includes or consists essentially of a phosphor layer orphosphor-containing layer, as shown in FIGS. 14A and 14B. FIGS. 15A and15B illustrate other embodiments featuring a first layer 1420 thatincludes or consists essentially of a transparent material such asbinder or matrix material 740, a second layer 1410 that includes orconsists essentially of a first phosphor layer or phosphor-containinglayer, and a third layer 1430 that includes or consists essentially of asecond phosphor layer or phosphor-containing layer. The first phosphorlayer or phosphor-containing layer is different from (i.e., includes orconsists essentially of a different phosphor material or a differentconcentration of the same phosphor material) the second phosphor layeror phosphor-containing layer.

In the above discussion, mold surface 200 (FIG. 3) is shown as flat;however, this is not a limitation of the present invention, and in otherembodiments mold surface 200 is concave, is convex, or has any arbitraryshape. In one embodiment, mold surface 200 is tilted or stepped to makephosphor chips 312 with different thicknesses. An example is shown inFIGS. 16A-16D, which depict a mold 230 having three different regions 1,2 and 3, each having a different depth. In one embodiment, the phosphorchip 311 is separated from the mold 230, and then phosphor chips 312 ₁,312 ₂ and 312 ₃ are separated from the different thickness phosphorlayers. The different-thickness phosphor chips 312 may be associatedwith LEEs 710 with different peak emission wavelengths and use LEEs 710with a relatively wide emission wavelength range. In another embodiment,the bottom surface 200 of mold 230 is slanted to provide a variation inthickness of phosphor chips 312. In another embodiment, mold 230 istilted to provide a variation in the thickness of phosphor chips 312.

In one embodiment, the thickness of phosphor 310, and thus the thicknessof phosphor chip 312, is controlled by feedback during the fillingprocess of mold 230. In one embodiment, phosphor 310 is excited by anappropriate pump source, for example a LEE such as a LED or laser, andthe resulting white-light color temperature measured. When the targetwhite-light color temperature is reached, the fill mechanism is notifiedto stop the filling of mold 230. FIG. 17 depicts an example of such anembodiment, with mold 230, a reservoir 1740 of phosphor 310, phosphor310 also in mold 230, a pump source 1710, and a detector 1720. Thetarget color temperature is compared to that measured by detector 1720,and when the target color temperature is reached, detector 1720 sends asignal to close valve 1730, stopping further dispensing of phosphor 310into mold 230. In some embodiments, detector 1720 and valve 1730 operatein an on-off configuration while in other embodiments they use aproportional control. In some embodiments, an offset in the timing orvalve-control signal is included to accommodate hysteresis or delays inthe mold-filling process. Mold 230 may be transparent or have atransparent region or window to a wavelength of light emitted by pumpsource 1710. FIG. 17 shows one configuration of such a filling controlscheme; however, other configurations may be employed, and the specificconfiguration is not a limitation of the present invention. In anotherembodiment, pump source 1710 may be above mold 230, rather than belowit. After phosphor 310 is deposited or dispensed, it may be cured andthe resulting structure processed as described elsewhere in thisdescription.

The approach described above provides various apparatus and methods tomake uniform phosphor chips 312, resulting in highly uniform opticalcharacteristics of phosphor chips 312 and LEEs 710. However, theuniformity of the optical characteristics may also depend on the opticalcharacteristics of the LEE 710, in particular its emission wavelength.Referring back to FIG. 6, even if the phosphor is perfectly uniform, avariation in LEE 710 emission wavelength may result in an increaseddistribution in color temperature and/or other optical characteristics.One approach is to test and sort, or bin, LEEs 710 to create groups ofLEEs 710 with relatively narrow distributions of opticalcharacteristics, for example emission wavelength, and to then createdifferent thickness or composition phosphor chips 312 to match theaverage optical characteristics of the group of LEEs 710.

In another embodiment, a first layer of phosphor 310 is formed and iscured, uncured or partially cured, and then a second layer of phosphor310 is formed over one or more portions of the initial phosphor that wasformed, in response to a need for varying thickness phosphor chips 312.A schematic of such a structure is shown in FIG. 18, which depicts afirst phosphor 1810 and a second phosphor 1820 thereover. In oneembodiment, this approach permits improvement of the uniformity of thetotal phosphor thickness, or reduces the uniformity requirement of firstphosphor layer 1810. Additionally, this provides a way to provide anengineered non-uniform phosphor chip, such as a non-uniform phosphorchip 312.

In another embodiment, a set of dividing grids is formed in mold 230prior to formation of phosphor 310. The grids divide phosphor 310 intosmaller regions, which after curing form phosphor chips 312. This is analternate approach to cutting or separation of the phosphor aftercuring.

The arrangement of phosphor chips 312 makes them amenable to transfer orpick-and-place operations of multiple units at a time. The techniquesdescribed here permit the formation of relatively large rectangular orsquare arrays, from which a multiple tool pick-and-place or stampoperation may be fed with almost 100% utilization of all phosphor chips312 in the array, where the pick or stamp pitch is, in some embodiments,an integer multiple of the pitch of phosphor chips 312 in the sourcearray.

In some embodiments, the approaches described above to make multiplephosphor chips 312 are combined with testing and sorting to produce binsor groups of phosphor chips 312 having relatively narrowly distributedcharacteristics. For phosphor chips such properties may be determinedalone or in combination with one or more LEEs 710. Such characteristicsmay include electrical characteristics such as forward voltage, leakagecurrent, etc., and/or optical characteristics such as color temperature,color rendering index, efficiency, light output power and the like.

The approaches described above may permit batch or bulk fabrication ofrelatively large numbers of phosphor chips 312 in an economical mannerwith relatively tight distributions of characteristics. In particular,these approaches lead to the manufacture of cost-effective phosphorchips 312, that when combined with LEEs 710, have relatively narrowcolor temperature variations. In some embodiments, these approaches leadto a plurality of combinations of phosphor chips 312 and LEE 710 havinga color temperature range of less than about five MacAdam ellipses, orless than three MacAdam ellipses, or less than two MacAdam ellipses oreven less than one MacAdam ellipse.

The methods described above may permit the manufacture of very largearrays of phosphor chips 312 in an economical manner with a relativelynarrow distribution in optical and mechanical characteristics. In someembodiments, the phosphor chip 312 has a side dimension of about 250 μmto about 5 mm and the kerf is about 10 μm to about 50 μm. In oneembodiment, phosphor chips 312 have a pitch of about 1000 μm. This leadsto a density of phosphor chips of about 1.0/mm² or about 100 phosphorchips 312 per square cm. The manufacturing approaches described abovemay be practiced on any arbitrary size area. In one embodiment the areais about 10 cm×about 10 cm, or about 1000 cm². In this example, thisleads to the ability to manufacture 100,000 phosphor chips 312simultaneously. This is just one example and not meant to be limiting tothe invention. In general the density of phosphor chips 312 may varywith the size of LEEs 710 to which they are associated, the kerf, andthe amount of phosphor desired on the sides of LEEs 710.

The above-described equipment, structures and methods may permit anintegrated approach to the manufacture of phosphor chips 312 in a batchprocess at relatively low cost. This approach may include testing andsorting and binning, as is done with conventional packaged white LEDs.Trimming may be employed to further narrow the distribution of phosphorchip characteristics. In contrast to conventional packaged white LEDs,this approach may produce phosphor chips 312 that are then combined withLEEs 710. This reduces the cost and complexity of using white LEDs. Afurther advantage of embodiments of the invention is the use of arelatively larger portion of the manufacturing output of LEEs 710,because it provides an economical and straightforward way to match thephosphor characteristics to those of LEEs 710, in order to produceuseful distributions of white light emitters.

In the structures described above, one or more surfaces of the phosphor,for example phosphor 311 or phosphor chips 312, may be patterned orroughened to improve light extraction from the phosphor, for example byreducing TIR in the phosphor. Such patterns or roughened or texturedsurfaces may be formed in a variety of ways. In one embodiment, theseare formed by molding. In one embodiment, these are formed by techniquessuch as, for example laser ablation, wet or dry chemical etching,grinding, drilling or the like. In one embodiment, these may be formedby selective curing of the phosphor 310. In one embodiment, thesefeatures may be an array, such as a regular periodic array like aphotonic crystal to aid in controlling the direction of the lightexiting the phosphor. In some embodiments, such texturing, patterning orthe like is present only on one surface, on one portion of one surface,or on multiple surfaces of the phosphor.

The systems described above may be combined with additional electronicsto form an electronic device 1900 as shown in FIG. 19. In oneembodiment, the device 1900 includes multiple LEEs 710 (incorporatingphosphor chips 312, not shown for clarity) that are electrically coupledto traces 730. As shown, electronic device 1900 includes threeserially-connected strings 1910 of LEEs 710. Electronic device 1900 alsoincludes circuitry 1920 electrically connected to one or more of strings1910. Circuitry 1920 may include or consist essentially of portions orsubstantially all of the drive circuitry, sensors, control circuitry,dimming circuitry, and or power-supply circuitry or the like, and mayalso be adhered (e.g., via an adhesive) or otherwise attached to asubstrate 1930. In one embodiment, the power supply and driver aredistributed, e.g., the device 1900 may have a centralized power supplyand all or a portion of the drive circuitry distributed in differentlocations. Circuitry 1920 may even be disposed on a circuit board (e.g.,a printed circuit board) that itself may be mechanically and/orelectrically attached to substrate 1930. In other embodiments, circuitry1920 is separate from substrate 1930. In some embodiments circuitry 1920is formed on substrate 1930. While FIG. 19 depicts the LEEs 710 andserially connected in strings 1910, and strings 1910 connected orconnectable in parallel, other die-interconnection schemes are possibleand within the scope of embodiments of the invention.

As shown in FIG. 19, the lighting system 1900 may feature multiplestrings, each string 1910 including or consisting essentially of acombination of one or more LEEs 710 electrically connected in series, inparallel, or in a series-parallel combination with optional fuses,antifuses, current-limiting resistors, zener diodes, transistors, andother electronic components to protect LEEs 710 from electrical faultconditions and limit or control the current flow through individual LEEs710 or electrically-connected combinations thereof. In general, suchcombinations feature an electrical string that has at least twoelectrical connections for the application of DC or AC power. A stringmay also include a combination of one or more LEEs 710 electricallyconnected in series, in parallel, or in a series-parallel combination ofLEEs 710 without additional electronic components. FIG. 19 shows threestrings of LEEs 710, each string having three LEEs 710 in series;however, this is not a limitation of the present invention, and in otherembodiments the number of strings is less than or greater than three andthe number of LEEs 710 in a string may be greater or less than three. Inone embodiment, a string includes at least ten LEEs 710. In oneembodiment a string includes at least 45 LEEs 710. In one embodiment,system 1900 includes at least ten strings, or even at least 50 strings.

In some embodiments, the lighting systems described above furtherfeature one or more optical elements. In some embodiments, one opticalelement is associated with each LEE 710, while in other embodimentsmultiple LEEs 710 are associated with one optical element, or multipleoptical elements are associated with a single LEE 710, or no engineeredoptical element is associated with any LEE 710, and the LEE (and/orphosphor associated therewith) has only a flat or roughened surface. Inone embodiment, the optical elements include features to scatter,diffuse and/or spread out light generated by the LEE 710 and/or phosphor312. The optical elements may be formed by etching, polishing, grinding,machining, molding, embossing, extruding, casting, or the like. Themethod of formation of the optical elements is not a limitation ofembodiments of the present invention.

FIGS. 20-22 present different embodiments of the present invention thatfeature one or more optical elements. In FIG. 20, each LEE 710 andassociated phosphor chip 312 has associated with it an optical element2020 (each depicted as a portion of an optic 2010). Optic 2010 typicallyfeatures an array of optical elements 2020; in some embodiments, oneoptical element 2020 is associated with each LEE 710, while in otherembodiments multiple LEEs 710 are associated with one optical element2020, or multiple optical elements 2020 are associated with a single LEE710, or no engineered optical element is associated with any LEE 710,for example optic 2010 may be only a plate with a flat or roughenedsurface. In one embodiment, optic 2010 includes elements or features toscatter, diffuse and/or spread out light generated by LEE 710 and/orphosphor chip 312.

Optic 2010 may be substantially optically transparent or translucent.For example, optic 2010 may exhibit a transmittance greater than 80% foroptical wavelengths ranging between approximately 400 nm andapproximately 600 nm. In one embodiment, optic 2010 includes or consistsessentially of a material that is transparent to a wavelength of lightemitted by LEE 710 and/or phosphor chip 312. Optic 2010 may besubstantially flexible or rigid. In some embodiments, optic 2010includes multiple materials and/or layers. Optical elements 2020 may beformed in or on optic 2010. Optic 2010 may include or consistessentially of, for example, acrylic, polycarbonate, polyethylenenaphthalate (PEN), polyethylene terephthalate (PET), polycarbonate,polyethersulfone, polyester, polyimide, polyethylene, glass or the like.Optical elements 2020 may be formed by etching, polishing, grinding,machining, molding, embossing, extruding, casting, or the like. Themethod of formation of optical elements 2020 is not a limitation of thepresent invention.

Optical elements 2020 associated with optic 2010 may all be the same ormay be different from each other. Optical elements 2020 may include orconsist essentially of, e.g., a refractive optic, a diffractive optic, aTIR optic, a Fresnel optic, or the like, or combinations of differenttypes of optical elements. Optical elements 2020 may be shaped orengineered to achieve a specific light distribution pattern from thearray of light emitters, phosphors and optical elements.

As used herein, “alignment” and “aligned” may mean that the center ofone structure, for example LEE 710, is aligned with the center ofanother structure, for example optical element 2010; however, this isnot a limitation of the present invention and in other embodimentsalignment refers to a specified relationship between the geometries ofmultiple structures.

The space between the back side of optic 2010 and phosphor chip 312,conductive traces 730 and LEE substrate 720, designated as region 2030in FIG. 20, may be a partial vacuum or be filled with air, filled with afluid or other gas or filled or partially filled with one or more othermaterials. In one embodiment, region 2030 is filled or partially filledwith a transparent material, similar to a material that may fill region740 or that is used as the binder for phosphor chip 312, to reduce TIRlosses in LEE 710 and to provide enhanced optical coupling betweenphosphor chip 312 and optic 2010.

In FIG. 21, optic 2010 incorporates depressions 2110 to accommodate orpartially accommodate phosphor chips 312. Phosphor chips 312 may beformed or inserted into depressions 2110, for example using apick-and-place tool. Phosphor chips 312 may be held in depressions 2110mechanically, and/or with an adhesive or glue. In one embodiment,phosphor chips 312 are held in place by a transparent material similarto the binder or matrix used in phosphor chip 312. In one embodiment,depression 2110 is larger than phosphor chip 312. In one embodiment,depression 2110 is sized to just accommodate phosphor chip 312. A region2120, similar to region 2030 in FIG. 20, may be a partial vacuum or befilled with air, filled with a fluid or other gas or filled or partiallyfilled with one or more other materials. In one embodiment, region 2120is filled or partially filled with a transparent material, similar to amaterial that may fill region 740 or that is used as the binder forphosphor chip 312, to provide reduced optical losses.

In FIG. 22 depressions 2110 in optic 2010 are curved such that phosphorchip 312 completely or substantially completely covers the top and sidesof LEE 710. The periphery of the structures shown in FIGS. 20-22 may besealed with an optional sealing material or materials. Such sealing mayprovide a barrier to external influences, for example humidity,corrosive ambients, etc. The seal may include or consist essentially of,for example, adhesive, glue, tape, or material such as that of material2030, material 740, LEE substrate 720, or the like.

The examples discussed above show one LEE 710 associated with eachphosphor chip 312. However, this is not a limitation of the presentinvention and in other embodiments a phosphor chip 312 is associatedwith multiple LEEs 710. Examples discussed above for phosphor chip 312show phosphor chip 312 as being square and having sidewallsperpendicular to the sidewalls. However, this is not a limitation of thepresent invention, and in other embodiments phosphor chip 312 isrectangular, hexagonal, circular, triangular, or any arbitrary shape,and/or has sidewalls forming any angle with respect to the surface ofphosphor chip 312.

While the phosphor chip has been used as part of a structure producingwhite light, this is not a limitation of the present invention, and inother embodiments, different color LEEs 710 and different phosphors (oneor more) may be used to produce other colors, for example amber, green,or any arbitrary color or spectral power distribution. In someembodiments, the multiple LEEs 710 are all the same, while in otherembodiments the multiple LEEs 710 include two or more groups ofdifferent LEEs 710, e.g., each emitting at different wavelengths.

Other embodiments of this invention have additional or fewer steps orcomponents or may be modified or carried out in a different order. Ingeneral in the above discussion the arrays of light emitters, wells,optics and the like have been shown as square or rectangular arrays;however, this is not a limitation of the present invention and in otherembodiments these elements are formed in other types of arrays, forexample hexagonal, triangular or any arbitrary array. In someembodiments, these elements are grouped into different types of arrayson a single substrate.

The terms and expressions employed herein are used as terms andexpressions of description and not of limitation, and there is nointention, in the use of such terms and expressions, of excluding anyequivalents of the features shown and described or portions thereof. Inaddition, having described certain embodiments of the invention, it willbe apparent to those of ordinary skill in the art that other embodimentsincorporating the concepts disclosed herein may be used withoutdeparting from the spirit and scope of the invention. Accordingly, thedescribed embodiments are to be considered in all respects as onlyillustrative and not restrictive.

What is claimed is:
 1. An electronic device comprising: a substratehaving a plurality of conductive traces on a surface thereof, each pairof conductive traces being separated on the substrate by a gaptherebetween; a plurality of light-emitting diode (LED) dies eachspanning a gap between conductive traces and having first and secondspaced-apart contacts each electrically coupled to one of the conductivetraces defining the gap; and a plurality of discrete phosphor chips,each phosphor chip (i) disposed over an LED die and positioned toreceive light therefrom, and (ii) attached to the LED die by anattachment agent discrete from the LED die and the phosphor chip,wherein each phosphor chip comprises (i) a light-conversion material and(ii) a binder comprising at least one of silicone or epoxy.
 2. Theelectronic device of claim 1, wherein the attachment agent comprises atleast one of a clip or a frame attached to the substrate.
 3. Theelectronic device of claim 1, wherein the attachment agent comprises anadhesion agent adhering the phosphor chip to the LED die.
 4. Theelectronic device of claim 3, wherein a transmittance of the attachmentagent for a wavelength emitted by the LED die is greater than 90%. 5.The electronic device of claim 3, wherein a transmittance of theattachment agent for a wavelength emitted by the LED die is greater than95%.
 6. The electronic device of claim 3, wherein the adhesion agentcomprises a transfer tape.
 7. The electronic device of claim 1, wherein(i) each phosphor chip has a thickness, and (ii) a variation in thethicknesses of the phosphor chips is less than ±5%.
 8. The electronicdevice of claim 1, wherein each phosphor chip absorbs at least a portionof light emitted from the LED die over which it is disposed and emitsconverted light having a different wavelength, converted light andunconverted light emitted by the LED die combining to form substantiallywhite light.
 9. The electronic device of claim 8, wherein thesubstantially white light emitted collectively from the different LEDdies and phosphor chips has a color temperature variation less than fourMacAdam ellipses.
 10. The electronic device of claim 8, wherein thesubstantially white light emitted collectively from the different LEDdies and phosphor chips has a color temperature variation less than twoMacAdam ellipses.
 11. The electronic device of claim 1, furthercomprising circuitry for powering at least one LED die.
 12. Theelectronic device of claim 1, further comprising circuitry forcontrolling optical output characteristics of at least one LED die andthe phosphor chip disposed thereover.
 13. The electronic device of claim12, wherein the optical output characteristic comprises at least one ofchromaticity, luminous flux, correlated color temperature, color point,or color rendering index.
 14. The electronic device of claim 1, furthercomprising an optical element associated with at least one LED die. 15.The electronic device of claim 1, wherein the first and second contactsare electrically coupled to conductive traces with a conductiveadhesive.
 16. The electronic device of claim 15, wherein the conductiveadhesive comprises an anisotropic conductive adhesive (ACA).
 17. Theelectronic device of claim 16, wherein (i) the ACA is disposed betweenthe LED die and the substrate, and (ii) the ACA electrically connects afirst conductive trace only to the first contact and a second conductivetrace, different from the first conductive trace, only to the secondcontact.
 18. The electronic device of claim 16, wherein a portion of theACA is disposed in the gap and substantially electrically isolates thefirst contact from the second contact.
 19. The electronic device ofclaim 1, wherein the first and second contacts are electrically coupledto conductive traces with at least one of wire bonds or solder.
 20. Theelectronic device of claim 1, wherein each LED die comprises a bare LEDdie.
 21. The electronic device of claim 1, wherein the light-conversionmaterial comprises a plurality of phosphor particles.
 22. The electronicdevice of claim 1, wherein a surface of the phosphor chip is textured.23. The electronic device of claim 1, wherein the phosphor chip definesan indentation into which the LED die is at least partially disposed.24. The electronic device of claim 1, wherein the conductive tracescomprise at least one of silver, gold, aluminum, chromium, copper, orcarbon.
 25. The electronic device of claim 1, wherein the substratecomprises at least one of polyethylene naphthalate, polyethyleneterephthalate, polycarbonate, polyethersulfone, polyester, polyimide,polyethylene, or paper.
 26. The electronic device of claim 1, wherein areflectivity of the substrate for a wavelength emitted by at least oneof the LED die or the phosphor chip is greater than 80%.
 27. Theelectronic device of claim 1, wherein a transmittance of the substratefor a wavelength emitted by at least one of the LED die or the phosphorchip is greater than 80%.
 28. The electronic device of claim 1, whereinthe LED die comprises a semiconductor material comprising at least oneof GaN, AlN, InN, or an alloy or mixture thereof. 29.-128. (canceled)